1. Technical Field
The present invention relates generally to cellular wireless communication networks; and more particularly to the transmission of high speed data communications in such a cellular wireless communication network.
2. Related Art
Wireless networks are well known. Cellular wireless networks support wireless communication services in many populated areas of the world. While wireless networks were initially constructed to service voice communications, they are now called upon to support data communications as well. The demand for data communication services has exploded with the acceptance and widespread use of the Internet. While data communications have historically been serviced via wired connections, wireless users are now demanding that their wireless units also support data communications. Many wireless subscribers now expect to be able to “surf” the Internet, access their email, and perform other data communication activities using their cellular phones, wireless personal data assistants, wirelessly linked notebook computers, and/or other wireless devices. The demand for wireless network data communications will only increase with time. Thus, wireless networks are currently being created/modified to service these burgeoning data communication demands.
Significant performance issues exist when using a wireless network to service data communications. Wireless networks were initially designed to service the well-defined requirements of voice communications. Generally speaking, voice communications require a sustained bandwidth with minimum signal-to-noise ratio (SNR) and continuity requirements. Data communications, on the other hand, have very different performance requirements. Data communications are typically bursty, discontinuous, and may require a relatively high bandwidth during their active portions. To understand the difficulties in servicing data communications within a wireless network, consider the structure and operation of a cellular wireless network.
Cellular wireless networks include a “network infrastructure” that wirelessly communicates with user terminals within a respective service coverage area. The network infrastructure typically includes a plurality of base stations dispersed throughout the service coverage area, each of which supports wireless communications within a respective cell (or set of sectors). The base stations couple to base station controllers (BSCs), with each BSC serving a plurality of base stations. Each BSC couples to a mobile switching center (MSC). Each BSC also typically directly or indirectly couples to the Internet.
In operation, a user terminal communicates with one (or more) of the base stations. A BSC coupled to the serving base station routes voice communications between the MSC and the serving base station. The MSC routes the voice communication to another MSC or to the public switched telephone network (PSTN). BSCs route data communications between a servicing base station and a packet data network that may couple to the Internet.
The wireless link between the base station and the user terminal is defined by one of a plurality of operating standards, e.g., AMPS, TDMA, CDMA, GSM, etc. These operating standards, as well as new 3G and 4G operating standards define the manner in which the wireless link may be allocated, setup, serviced and torn down. These operating standards must set forth operations that will be satisfactory in servicing both voice and data communications.
The wireless network infrastructure must support both low bit rate voice communications and the varying rate data communications. More particularly, the network infrastructure must transmit low bit rate, delay sensitive voice communications together with high data rate, delay tolerant rate data communications. While voice communications typically have a long hold time, e.g., remain active for longer than two minutes on the average, high data rate/delay tolerant data communications are bursty and are active only sporadically. As contrasted to the channel allocation requirements of voice communications, channels must be frequently allocated and deallocated to the data communication in order to avoid wasting spectrum. Such allocation and deallocation of channels to the data communications consumes significant overhead.
Further, because voice communications must have priority over data communications, the data communications often can be allocated little or no resources. Not only must data users compete with voice users for channels, they must compete with the other data users for the channels as well. In most operating scenarios, it is very difficult to obtain a channel and to maintain the channel to fully service the data communication. If the channel allocation is prematurely deallocated by the network infrastructure, the data communication will be interrupted causing a protocol layer above the physical layer of the wireless link to fail.
The cellular wireless industry is currently addressing concerns relating to data communications. Because data communications typically require significantly more bandwidth on the forward link than on the reverse link, various standards have been promoted to provide for a high data rate forward link. For example, in the 3GPP standards body, the high data rate down link packet access (HSDPA) standard has been promulgated. This HSDPA standard is a UMTS evolution standard, which will be released sometime in 2001. Likewise, the 3GPP2 standards body has released various standards that support high data rate forward link transmissions. One such standard is the 1xEV-DO standard that provides for data only high data rate forward link transmissions as therein described. This standard is also referred to as the “HDR Air Interface (HAI) Specification.
According to the HAI Specification, transmission on a single high speed Forward Channel (F-CH) is Time Division Multiplexed (TDM). At any given time in its operation, the F-CH is either being transmitted or not, and if it is being transmitted, it is addressed to a single user terminal. However, the HAI Specification is limited with regard to data rates and encoder data packet sizes. Because only a single user terminal at a single data rate may be addressed at any time, only a portion of an encoder packet may be used for the single user. In such case, the remaining portion of the encoder packet is empty or filled with duplicate data. Therefore, a portion of the high speed F-CH is oftentimes wasted.
It would therefore be desirable to provide a communication system that is capable of carrying high speed data communications with minimal waste of spectral capacity.